使用 c# 替换密码区分大小写

Question

我想制作一种加密方法，它可以在纯文本变量中接受大写和小写，比如（“Hello World）它只接受小写字母，请帮助我，我想 它工作正常，只有小写字母作为输入，请帮助我

            using System;

        class SubstitutionCipher
        {
           static void Main()
           {
              string key = "jfkgotmyvhspcandxlrwebquiz";
              string plainText = "the quick brown fox jumps over the lazy dog";
              string cipherText = Encrypt(plainText, key);
              string decryptedText = Decrypt(cipherText, key);
              Console.WriteLine("Plain     : {0}", plainText);
              Console.WriteLine("Encrypted : {0}", cipherText);
              Console.WriteLine("Decrypted : {0}", plainText);
              Console.ReadKey();
           }
    //encryption method 
           static string Encrypt(string plainText, string key)
           {
              char[] chars = new char[plainText.Length];
              for(int i = 0; i < plainText.Length; i++)
              {
                 if (plainText[i] == ' ')
                 {
                    chars[i] = ' ';
                 }   
                 else
                 {
                    int j = plainText[i] - 97;
                    chars[i] = key[j];
                 }
              }
              return new string(chars);
           }
//decryption method
           static string Decrypt(string cipherText, string key)
           {
              char[] chars = new char[cipherText.Length];
              for(int i = 0; i < cipherText.Length; i++)
              {
                 if (cipherText[i] == ' ')
                 {
                    chars[i] = ' ';
                 }   
                 else
                 {
                    int j = key.IndexOf(cipherText[i]) - 97;
                    chars[i] = (char)j;
                 }
              }
              return new string(chars);
           } 
        }

Answer 1

这是一个有趣的问题，尤其是在一般情况中。所以我们有

1. 密钥中的字符，这些字符应加密（例如a、j）
2. 不在键中的字符，应该跳过这些字符（例如空格）

为了高效，让我们设计一个Encryptor\Decryptor为Dictionary<Char, Char>，为了做到这一点，我们应该对key中的字符进行排序并进行对应； 例如对于

  key        = "jfkgo"
  sorted key = "fgjko"

这对将是

  {j, f} // when encrypting "j" becomes "f", on decryption "f" turns into "j"
  {f, g}
  {k, j}
  {g, k}
  {o, o}

当读取从左到右我们有一个加密器，当读取从右到左一个解密器：

private static Dictionary<Char, Char> Encryptor(String key) {
  Char[] data = key.ToArray();
  Char[] sorted = data.OrderBy(c => c).ToArray();

  return data
    .Zip(sorted, (plain, encrypted) => new {
         Plain = plain,
         Encrypted = encrypted
     })
    .ToDictionary(item => item.Plain, item => item.Encrypted);
}

// Note, that Decryptor is the same as Encryptor by for the last line
private static Dictionary<Char, Char> Decryptor(String key) {
  Char[] data = key.ToArray();
  Char[] sorted = data.OrderBy(c => c).ToArray();

  return data
    .Zip(sorted, (plain, encrypted) => new {
      Plain = plain,
      Encrypted = encrypted
    })
    .ToDictionary(item => item.Encrypted, item => item.Plain);
}

现在，很容易实现加密和解密方法

private static String Encrypt(String source, String key) {
  var dict = Encryptor(key);

  StringBuilder Sb = new StringBuilder(source.Length);

  Char sub;

  foreach (var ch in source)
    if (dict.TryGetValue(ch, out sub))
      Sb.Append(sub);
    else
      Sb.Append(ch);

  return Sb.ToString();
}

 // Note, that Decryptor is the same as Encryptor by for the first line
private static String Decrypt(String source, String key) {
  var dict = Decryptor(key);

  StringBuilder Sb = new StringBuilder(source.Length);

  Char sub;

  foreach (var ch in source)
    if (dict.TryGetValue(ch, out sub))
      Sb.Append(sub);
    else
      Sb.Append(ch);

  return Sb.ToString();
}

一个小测试

 // For test, let capital letters mmimic the small ones
 string key = "jfkgotmyvhspcandxlrwebquiz" + "jfkgotmyvhspcandxlrwebquiz".ToUpper();

 string plainText = "The Quick Brown Fox Jumps Over The Lazy Dog!";
 string cipherText = Encrypt(plainText, key);
 string decryptedText = Decrypt(cipherText, key);

 Console.WriteLine("Plain     : {0}", plainText);
 Console.WriteLine("Encrypted : {0}", cipherText);
 Console.WriteLine("Decrypted : {0}", plainText);

Answer 2

您要减去“a”，这仅适用于小写字符。您应该检查它是大写还是小写，然后分别减去 A 或 a。此外，您可以直接使用 'a' 或 'A' 来获得 int 等效的字符。

我的意思是在你的 else 语句中使用它来解密和加密：

    static string Encrypt(string plainText, string key)
    {
        char[] chars = new char[plainText.Length];
        for (int i = 0; i < plainText.Length; i++)
        {
            if (plainText[i] == ' ')
            {
                chars[i] = ' ';
            }
            else if (Char.IsUpper(plainText[i]))
            {
                int j = plainText[i] - 'A';
                chars[i] = key[j];
            }
            else
            {
                int j = plainText[i] - 'a';
                chars[i] = key[j];
            }
        }
        return new string(chars);

    static string Decrypt(string cipherText, string key)
    {
        char[] chars = new char[cipherText.Length];
        for (int i = 0; i < cipherText.Length; i++)
        {
            if (cipherText[i] == ' ')
            {
                chars[i] = ' ';
            }
            else if (Char.IsUpper(cipherText[i]))
            {
                int j = key.IndexOf(cipherText[i]) - 'A';
                chars[i] = (char)j;
            }
            else
            {
                int j = key.IndexOf(cipherText[i]) - 'a';
                chars[i] = (char)j;
            }
        }
        return new string(chars);
    }

或分别用于加密和解密的简短版本：

            else 
            {
                int j = Char.IsUpper(plainText[i]) ? plainText[i] - 'A' : plainText[i] - 'a';
                chars[i] = key[j];
            }

            else
            {
                int j = Char.IsUpper(cipherText[i]) ? key.IndexOf(cipherText[i]) - 'A' :  key.IndexOf(cipherText[i]) - 'a';
                chars[i] = (char)j;
            }

编辑：

好的，我认为算法已经完成了，我刚刚修复了会导致异常的部分。但是，您是：

a) 不考虑哪个字母大写和 b) 没有可用的解密器。 （我认为它有效，但是您的主要方法将明文结果作为解密消息）。

要修复您的解密器，您需要在加密器上添加一种存储大写字母的方法。您可以对它进行更复杂的处理，但目前，我们将其加密为密文上的大写字母。

    static string Encrypt(string plainText, string key)
    {
        char[] chars = new char[plainText.Length];
        for (int i = 0; i < plainText.Length; i++)
        {
            if (plainText[i] == ' ')
            {
                chars[i] = ' ';
            }
            else 
            {
                int j = Char.IsUpper(plainText[i]) ? plainText[i] - 'A' : plainText[i] - 'a';
                chars[i] = Char.IsUpper(plainText[i]) ? Char.ToUpper(key[j]) : key[j];
            }
        }
        return new string(chars);

要解密，您应该在密钥上找到它作为小写字符，但输出为大写字符。

    static string Decrypt(string cipherText, string key)
    {
        char[] chars = new char[cipherText.Length];
        for (int i = 0; i < cipherText.Length; i++)
        {
            if (cipherText[i] == ' ')
            {
                chars[i] = ' ';
            }
            else
            {
                int j = Char.IsUpper(cipherText[i]) ? key.IndexOf(Char.ToLower((char)cipherText[i])) + 'a' : key.IndexOf(cipherText[i]) + 'a';
                chars[i] = Char.IsUpper(cipherText[i]) ? Char.ToUpper((char)j) : (char)j;
            }
        }
        return new string(chars);
    }